After long investigations [1]}, [2]}, [3]}
which revealed a deeper structure of the form factors of the Sine-Gordon model, Smirnov [4]} formulated the equivalent of axioms \(\mathrm {i)-ii)}\)  in that model.
Subsequently, Kirillov and Smirnov [5]} proposed the full set of the bootstrap program axioms, exemplified
in the case of the Massive Thirring model. See also [6]}
